In xerographic copying, a negative image of a document to be copied is formed on an electrically charged plate with toner, a fine, black, resinous powder. The sheet on which the copy is to be made is advanced over the plate and toner is transferred to the sheet by means of electrostatic forces. The sheet is then advanced to a fixing unit wherein the toner is fixed onto the sheet by radiant heating. The heating is sufficient to melt the resin of the toner so that it will permanently adhere to the sheet. The temperature required to fix conventional toners onto such sheets may be as high as 250.degree. C. or even higher.
The sheets which are used in such copiers must have sufficient thermal stability to withstand the fixing temperatures. The sheets must also have a sufficient coefficient of friction and mechanical strength to enable the sheet to be advanced through the copying machine and further, must have a surface on which the toner will adhere. Paper sheets, of sufficient thickness, are satisfactory for this purpose and have found widespread use in such copying machines. Paper, however, can be easily torn and has little resistance to staining or soiling. Thus, for certain applications, paper is not desired.
Certain plastic films, on the other hand, have superior mechanical strength and are more resistant to staining and soiling than paper and would be preferred for these applications. Such plastic films, however, tend to lack either the thermal stability or coefficient of friction necessary for use in such copiers. Such plastic films also tend to lack the ability to accept and anchor the xerographic toner on their surface.